Masonry units, sometimes referred to as concrete masonry units (CMUs), include segmental retaining wall (SRW) units, pavers, and architectural blocks, all of which are made from a "masonry concrete," which is comprised of hydratable cement binder and a fine aggregate. As used herein and hereinafter, the term "fine aggregate" means and refers to aggregate (e.g., non-cementitious) particles wherein at least 95% of said particles have an average diameter of less than 0.375 inches (0.95 cm.). Masonry concrete lacks the coarse aggregate (typically greater than 0.5 inch diameter) that is further used in conventional concrete, such as, for example, ready-mix concrete.
More significantly, masonry concrete differs from conventional concrete because it is said to have zero "slump," or, to phrase it more accurately, a practically immeasurable fluidity. The slump property is determined by placing wet masonry concrete into an inverted cone, and then removing the cone, and measuring the distance (if any) by which the cone-molded sample drops in height. See ASTM C143 (1988) ("Standard Test Method for Slump of Portland Cement Concrete"). Typically, the slump of masonry concrete is 0-0.75 inches, and thus masonry concrete is said to have essentially "zero slump."
The phenomenon of efflorescence is manifested as an undesirable whitish coloration or deposit on the surface of cement masonry units such as blocks, pavers, retaining wall segments, and other structures made of low-slump, cementitious mixtures. Efflorescence is a primary problem where the masonry units are used for aesthetic applications.
Currently available chemicals used for efflorescence control include the use of stearates (e.g., zinc stearate dispersions, calcium stearate dispersions) and tall oil fatty acid (TOFA), which, the inventors believe, hinders or blocks the water-borne movement of soluble salts such as calcium hydroxide to the surface of the masonry unit, thereby blocking one of the mechanisms by which efflorescence occurs.